<operating system> A means of communication between a program and its user, based solely on textual input and output. Commands are input with the help of a keyboard or similar device and are interpreted and executed by the program. Results are output as text or graphics to the terminal. Command line interfaces usually provide greater flexibility than graphical user interfaces, at the cost of being harder for the novice to use. Consequently, some hackers look down on GUIs as designed For The Rest Of Them. (1996-01-12)

A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and providing information to them as to what actions they are to perform.

command interpreter

<operating system> A program which reads textual commands from the user or from a file and executes them. Some commands may be executed directly within the interpreter itself (e.g. setting variables or control constructs), others may cause it to load and execute other files. Unix's command interpreters are known as shells. When an IBM PC is booted BIOS loads and runs the MS-DOS command interpreter into memory from file COMMAND.COM found on a floppy disk or hard disk drive. The commands that COMMAND.COM recognizes (e.g. COPY, DIR, PRN) are called internal commands, in contrast to external commands which are executable files. (1995-03-16)

<software> (Or "option", "flag", "switch", "option switch") An argument to a command that modifies its function rather than providing data. Options generally start with "-" in Unix or "/" in MS-DOS. This is usually followed by a single letter or occasionally a digit. More recently, GNU software adopted the --longoptionname style, usually in addition to traditional, single-character, -x style equivalents. Some commands require each option to be a separate argument, introduced by a new "-" or "/", others allow multiple option letters to be concatenated into a single argument with a single "-" or "/", e.g. "ls -al". A few Unix commands (e.g. ar, tar) allow the "-" to be omitted. Some options may or must be followed by a value, e.g. "cc prog.c -o prog", sometimes with and sometimes without an intervening space. getopt and getopts are commands for parsing command line options. There is also a C library routine called getopt for the same purpose. (2007-02-18)

A console application is a computer program designed to be used via a text-only computer interface, such as a text terminal, the command-line interface of some operating systems (Unix, DOS, etc.) or the text-based interface included with most graphical user interface (GUI) operating systems, such as the Windows Console in Microsoft Windows, the Terminal in macOS, and xterm in Unix.

In computing, an interface is a shared boundary across which two or more separate components of a computer system exchange information. The exchange can be between software, computer hardware, peripheral devices, humans, and combinations of these.

Command guidance is a type of missile guidance in which a ground station or aircraft relay signals to a guided missile via radio control or through a wire connecting the missile to the launcher and tell the missile where to steer to intercept its target. This control may also command the missile to detonate, even if the missile has a fuze.

(interfaces, interfacing, interfaced)